In commercial microwave ovens, which are most heavily used than domestic microwaves ovens, spits of food can become deposited around the oven, particularly on the inside walls of the oven. Unless these deposits are scrupulously cleaned off at the end of the day, they can build up to the extent that they desiccate and cause arcing and/or other damage. Subsequent repairs can be expensive.
Lightweight, disposable oven liners have been proposed. However, such a liner is of little practical use in a heavily used commercial oven.